Such a microdosing device is known from U.S. Pat. No. 6,196,219 B1. The known microdosing device has an atomizing unit in which is provided a dosing chamber for receiving a liquid quantity to be delivered. The dosing chamber is closed on one side by a membrane provided with several discharge openings in the form of perforations. With the facing boundary surface is associated a piezoelectric actuator serving as a vibrating unit. Into the dosing chamber issues a supply channel, which guides the liquid quantity required for a discharge process from a larger storage reservoir into the dosing chamber. During an activation of the vibrating unit, i.e. the piezoelectric actuator, the boundary surfaces of the dosing chamber and preferably also the membrane vibrate, so that the liquid quantity in the dosing chamber is atomized through the discharge openings of the membrane and consequently discharged. Even after the end of the actual discharge process the piezoelectric actuator continues to operate in order to heat the dosing chamber and thereby bring about a drying and evaporation of any liquid residues left behind.
EP 682 570 B1 discloses a further dosing device in which the liquid is delivered to the outside as an atomized spray mist through a perforated membrane from a storage area, in that the membrane is vibrated by vibrating means. Also in the case of this dosing device the vibrating means are operated longer than the time necessary for delivering the dosed liquid quantity. This is intended to deliver from the storage area the entire liquid quantity.
The problem of the invention is to provide a microdosing device of the aforementioned type permitting a precisely time-defined dosing of a liquid quantity.